The presence of foam creation during filling of containers with liquid products is a significant barrier to increasing rates of filling for mass produced liquid product packing lines. Foaming also results in the need for large bottle head space, especially with low viscosity liquids, to insure that the foam will be contained when the container is full and will not spill over on to the outside surface of the container. This requires more container material to be used than would otherwise be necessary in the absence of foam creation. Applicant has determined that the dominant mechanism in foam creation is the impingement of flow stream surface perturbations upon the standing pool of liquid in the container as it is being filled. Turbulent flow from the filling nozzle is the source of these perturbations. Prior art nozzles have attempted to minimize perturbations, but with significant limitations; these prior art nozzles will be discussed in turn.
Downflow nozzles incorporating fine screens tend to reduce turbulent eddies in flowing fluids. The small orifice size in the screens accomplishes this by physical restriction of the eddies. However, this does not eliminate turbulence; it only reduces it. To some degree the screens become a source of new turbulence by "tripping" transitional flow into the turbulent regime. Screen maintenance is also a limitation due to clogging and breakage of the screen.
Overflow filling uses a nozzle that enters and seals with the top of the container; the product is allowed to overflow the container. Because foam is less dense than liquid, the foam rises to the top of the container and into the product overflow. There is no reduction in foaming, only a method of dealing with foam after its creation. This method adds time to the filling cycle; the overflow foam must be recycled via a recycle loop in the process, unless you choose to throw the overflow away.
Side ported nozzles work by extension of part of the nozzle into the container. The fluid is then gently directed toward the inside walls of the container and allowed to cascade down the walls creating laminar flow. The flow velocity (upon impingement with the standing pool of fluid) is also reduced since the flow's cross sectional area increases as it coats the inside of the container. This method is complex to execute because nozzle design is dependent on container geometry. Also, product cannot be filled to the top of the container because of the fact that the nozzle must enter the container.
Submerged filling works by submerging the nozzle tip beneath the fluid level in the container. This eliminates the turbulence producing interaction inherent in the flow stream/air/standing pool interface present with all other types of filling. The maximum rate is limited as the descending stroke of the nozzle reduces overall cycle time. Product spillage on the containers is also a concern because the exterior of the nozzle is wetted in this method. This method requires extra time to enter and exit the container with the nozzle, is mechanically complex resulting in more costly equipment, uses mesh filter screens which clog, and may result in product spillage on the nozzle and bottle which is unsightly and unsanitary.
Laminar flow maintenance nozzles maintain laminar flow from a laminar fluid source, such as a reservoir filler. There is no development of laminar flow, only maintenance of preexisting laminar flow. This is not compatible with filling sources that are inherently turbulent, such as piston or flow meter dosing technology. The nozzle disclosed in U.S. Pat. No. 5,228,604 by Zanini et al., incorporated herein by reference, is such a nozzle. The Zanini et al. nozzle is a downflow nozzle that works without screens, but it is meant for use exclusively with reservoir filling sources, and is unable to convert turbulent flow to laminar flow.
No fluid nozzle filling technology is known that provides for laminar flow when a turbulent fluid source is used. Thus, there exists a need for a fluid nozzle that will develop laminar fluid flow from a turbulent flow source. The benefits of the present invention include that it provides for faster filling line speed, and a smaller necessary head space in the container which allows a reduction in the amount of container material.